Aza-[4 + 2] annulations of α-vinyl Morita–Baylis–Hillman adducts for regiodivergent synthesis of exomethylene-bearing azatricyclic compounds†
Abstract
Aza-[4 + 2] annulation reactions between α-vinyl Morita–Baylis–Hillman (MBH) adducts and cyclic imines have been developed, achieving regiodivergent synthesis of two distinct types of azatricyclic products. The process initiates with an SN2′′ addition of triphenylphosphine to the MBH adducts, forming a pentadienyl phosphonium intermediate. This intermediate then undergoes aza-[4 + 2] annulation with saccharin-derived ketimines to yield sultam-fused tetrahydropyridines with exomethylene groups in moderate to good yields. Alternatively, employing DABCO and trifluoroacetic acid facilitates an aza-[4 + 2] annulation with 3,4-dihydroisoquinoline, resulting in the formation of exomethylene-bearing benzoquinolizidines with reversed orientational regioselectivity.
![Graphical abstract: Aza-[4 + 2] annulations of α-vinyl Morita–Baylis–Hillman adducts for regiodivergent synthesis of exomethylene-bearing azatricyclic compounds](/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=D4QO00255E&imageInfo.ImageIdentifier.Year=2024)
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